diff --git a/4.SmartPointers/item18.md b/4.SmartPointers/item18.md
index 7abd057..6cf2386 100644
--- a/4.SmartPointers/item18.md
+++ b/4.SmartPointers/item18.md
@@ -31,14 +31,14 @@
 
 ```cpp
 class Investment { ... };
-class Sock: public Investment {...};
+class Stock: public Investment {...};
 class Bond: public Investment {...};
 class RealEstate: public Investment {...};
 ```
 
 ```mermaid
 classDiagram
-	Investment <|-- Sock
+	Investment <|-- Stock
 	Investment <|-- Bond
 	Investment <|-- RealEstate
 ```
@@ -121,7 +121,7 @@ makeInvestment(Ts&& params)
 
 ```cpp
 template<typename... Ts>
-makeInvestment(Ts&& params)
+auto makeInvestment(Ts&& params)
 {
   auto delInvmt = [](Investment* pInvestment)
 	{
@@ -187,4 +187,4 @@ std::shared_ptr<Investment> sp = makeInvestment(arguments);
 
 - `std::unique_ptr`是轻量级、快速的、只能move的管理专有所有权语义资源的智能指针
 - 默认情况，资源销毁通过delete，但是支持自定义delete函数。有状态的删除器和函数指针会增加`std::unique_ptr`的大小
-- 将`std::unique_ptr`转化为`std::shared_ptr`是简单的
\ No newline at end of file
+- 将`std::unique_ptr`转化为`std::shared_ptr`是简单的